Timing device for folding machines



July 25, 1950 DQRAN 2,516,454

TIMING DEVICE FOR FOLDING MACHINES Filed Dec. 26, 1947 2 Sheets-Sheet 1 INVENTOR THOMAS J, DORAN ATTORNEYS TIMING DEVICE FOR FOLDING MACHINES 2 Sheets-Sheet 2 Filed Dec. 26, 1947 Sla 52a Sin INVENTOR THOMAS J. DORAN FlG-E ATTORNEYS Patented July 25, 1950 UNITED STATES PATENT OFFICE TIMING DEVICE FOR FOLDING MACHINES Application December 26, 1947, Serial No. 793,806

Claims. I

The invention relates to a novel and improved timing device for the performance of an operation at a preselected point on a traveling article, and it relates more specifically to a timing device for performing a proportional folding operation on fiat work such as paper sheets, or laundry towels, sheets or the like.

Electronic time delay relays are now known in the art for effecting proportional folding operations. For example, in U. S. Patent Number 2,374,779, issued May 1, 1945, to John E. Preston, there is disclosed electronic time delay means involvin a time control responsive to discharge of a capacitor at different rates over different successive time periods, whereby a folding element, responsive to completion of such discharge, effects one or more proportionate folds in each of a succession of moving articles, permissibly of varying lengths. By means of Prestons control, each such article can be automatically folded at its mid point, or at two points such as the half and quarter length points, etc., or at other proportional intervals regardless of variations in length, within a permissive range. Certain embodiments of the Preston control are dependent upon the discharge of one or more capacitors before the execution of the folding operation.

As may be determined from an examination of the aforementioned Preston U. s. Patent Number 2,374,779, an article which is to be folded for example at its mid point, itself initiates discharge of the control capacitor when its leading edge operates a trip in the path of travel. The duration of time delay between such initiation of discharge and completion of the discharge to produce the desired operation is varied by the fact that the capacitor is permitted to discharge at different rates depending on article length, the change from a slow rate to an accelerated rate, for example, being initiated by passage of the trailing edge of the article past a trip in the path of travel. Fig. of the Preston patent discloses electronic means in an electrical circuit whereby a single proportionate fold may be effected in a "moving article such as a towel or sheet, regard- It is apparent, however, that in the embodiment shown in Fig. 10 and other figures of the aforesaid Preston patent, if the leading edge of a succeeding article intercepts the trip before completion of the operation on the preceding article, it not only nullifies the proper timing on th preceding article, but the capacitor is not permitted to again recharge. In this event the operation is not properly performed on two successive articles in the moving line. For successful operation of this and certain other of the embodiments in the aforesaid Preston patent, sufficient time must elapse after operation of the control trip, not only to permit completion of the first operation but also to allow sufficient additional time for recharging of the capacitor or capacitors for the second operation. While the time required for such recharge is only momentary, a train of articles moves relatively rapidly with the conveying means, and successive articles must be spaced far enough apart to permit discharge and recharge before each succeeding article operates the trip.

An object of the present invention is to provide time control means permitting quite minute spacing between each of a plurality of articles in succession in a moving line, while insuring an effective and accurate proportioned operation on each article. By the term proportioned or proportional as used herein, I mean an operation at the half point, or quarter point, or elsewhere fractionally of the article length.

A further object of the present invention is to provide means such as specified in the last preceding paragraph, whereby two separate and distinct timing operations on two successive articles can take place with a mutual chronological overlap, so that at least parts of both said timing operations may proceed simultaneously.

A further object of the invention is to provide an electronically controlled laundry fiatwork folder comprising a pair of folding control units, each unit being complete and distinct, and being individually adapted to control the proportioned folding of an article, in conjunction with article folding means, and selector means energized successively by passage of each of several articles on a conveyor, said selector means being adapted to render said folding means responsive, alternately, first to one said control unit, and then to the other said control unit.

Further objects of the invention are in part obvious, or will become apparent upon a study of the following specification in conjunction with the accompanying drawings in which Fig. 1 is a schematic showing of the essential elements of a machine for executing a single fold in a piece of laundry flat work;

Fig. 2 is a representation, partly diagrammatic and partly schematic, showing one embodiment of my invention, and

Fig. 3 shows somewhat conventionally, one embodiment of a snap-over device such as is used herein.

As representative of an operation to be performed, I have selected the folding of a pieceof laundry fiatwork at a point proportionate to its length, for example in the middle. It will be obvious as the description proceeds that the inventive concept may be utilized to perform other than folding operations at proportioned points on a series of moving articles- Referring to the folding machine as shown schematically in Figs. l and 2, each towel in a series to be folded is advanced from right to left on an endless conveyor it. Each towel in succession passes a trigger zone, and its leading edge interrupts electrical contacts through three trips ll, 12 and 13 so as to open respective electrical circuits. When the trailing edge passes the trips, the circuits are again closed. From the trips each towel advances to a folding zone where it is folded by mechanism responsive to trip operation, and later to be described. Trip l I is a selector trip for alternately selecting one or the other of two electronic control units A and B. Trip l2 cooperates with trip H in utilizing unit A for the execution of a timed folding operation on a first towel, and trip I3 cooperates with trip II in utilizing unit B for a like operation on the next towel. In the embodiment shown the three trips are arranged in a line transverse to the direction of travel of the towel, so as to be operated substantially simultaneously.

By means of this arrangement, and the circuits to be later described, if a time control unit A is timing a towel for an ultimate folding operation, and a second towel follows closely, it will not interfere with the timing operation on the first towel since unit B is then selected to come into operation and take up the task of timing the folding operation on the second towel. As will further appear, when the control is based upon the complete discharge of a condenser prior to operation of the folding means, and subsequent recharge for another operation, the use of two complete and distinct timing units, operating alternately, allows each unitample time for condenser discharge and recharge before it is again called upon to initiate another timing operation. It will be apparent that operation of the control units may be based upon timing means other than capacitance discharge, while still embodying my invention whenever the advantages hereinabove enumerated are obtained by the use of alternately energized units.

Selector trip II, when permitted to close by passage of the trailing edge of a towel, energizes a snap-over arrangement in housing l5 responsive to the closing of a circuit from L1 to L2 so as to throw armature l6 across the gap between the a and'b positions. The operation of this snap-over device will be more fully explained later in conjunction with Fig. 3. It will be understood that when in a position it is in operative relationship with control unit A, and when in 2) position it is in operative relationship with control unit B. It will also be further understood that interception of trip H by the leading edge of a towel merely breaks the electric-power supply to the snap-over means l5 and causes no operation of the snap-over mechanism. It will be further understood that armature l6 reverses its position each time the trailing edge of a towel passes trip II.

The folding mechanism comprises a folding blade it! operated by energization of a solenoid within housing I9. Energization of the solenoid produces movement of an armature (not shown) operatively linked to the folding blade. Each stroke of the folding blade closes a micro switch 20 in circuit with a switch-reversing arrangement indicated at 2! and energized by a circuit L1L2 which throws the switch armature 22 from contact a to contact I) or vice versa. Switch armature 22, and switch armature it previously described, mutually cooperate as will appear.

Since unit A and unit B are identical in structure, description of one will suffice, with special reference to Fig. 2.

Tubes 25 and 2B are separate heater type A. C. triodes, grid-controlled to pass anode-cathode or plate-current when the grid bias is within a specific range, but to cut off the plate current when the bias exceeds a critical or cut-off point.

The grid of tube 25 is normally biased from the secondary of the transformer 28, through resistor 29, to permit plate current to pass so as to energize relay coil 30. When trip 12 is in its normally closed position, however, an excess grid bias is applied to tube 25 from voltage divider3l through conductors 32 and 33, trip l2, conductorst l, 35, and 36, resistor 29 to the grid of tube 25 and from the grid through the cathode and conductor 3'! to the voltage divider. This gridcathode current flows only during the half cycle when the grid is positive with respect to the oathode. This cuts off plate current in tube 25 and deenergizes relay 30. Opening and closing of trip l2 by the leading and trailing edges, respectively, of a moving towel therefore produces, respectively, energization and deenergization of relay coil 38.

A similar result is produced on relay coil 38a, in unit B, by operation of trip l3, except when trip 13 isshunted by armature it, as shown.

The grid of tube 26 is at normal bias when capacitor 39 is fully discharged, by means to be later described. When thus normally biased tube 26passes plate current from the secondary wiring 48 of transformer 28 through conductors 4| and 42, relay 4%, conductors 44 and 45, plate to cathode of tube 26, and conductors 36,41, and 3'! back tosecondary wiring 40. Energization and de-energization' of relay coil 43 is therefore responsive, respectively to the discharged or charged condition of capacitor 39, since when the capacitor is charged it overbiases the grid of tube 26 to terminate plate current to relay 53.

A cycle of operations involving the performance of a folding operation on two successive towels in a moving row will now be described.

To start the cycle, assume that the machine has been shut down, that capacitor 39 is fully discharged, that switch armature I5 is in b position (as shown) and that switch armature '22 is in a position, as shown. The reason for switch armature I6 being in "11 position will appear as the description of the cycle proceeds. Ihe current supply from the line is now turned on to energize transformer 23 and heat the filaments of all tubes. Since trip I2 is closed, tube 25 is overbiased, and armature 5B of relay 30 is in its 1) position as shown. Since capacitor 39 is discharged, tube 26 is normally biased, and

relay 43 is energized by passage of plate current, placing its coupled armatures 5|, 52 and 53 in their a positions.

Under the conditions just outlined, as soon as the line switch is turned on, capacitor 39 begins to charge from voltage divider 3| in the secondary of transformer 28 through conductors 37 and 47, cathode and grid of tube 26, capacitor 39, conductors 55 and 56, armature 53 in a position, and conductor 5! to the voltage divider. The capacitor 33 rapidly acquires maximum charge, and consequently exceeds the tube-operating bias value of tube 26, so that tube 26 is blocked, and relay 43 would normally be deenergized. The relay remains energized, however, because of a maintaining circuit including trip I2 and relay armature 52 as follows; from the transformer secondary through conductors 4| and 42, relay coil 43, conductors 44 and 38, armature 52, conductors 54, 35, and 34, trip l2, and conductors 33 and 32, so that the relay coil 43 remains energized, armature 53 remains in "a position, and the charging effect is maintained.

Assume that a towel T approaches from the right on conveyor Ill, and its leading edge simultaneously intercepts trips |2 and I3. The opening of trip |2 breaks the maintaining circuit of relay 43, and its armatures all fall to their b position. Opening of trip it! also removes the excess bias of tube 25, as hereinbefore explained, the tube passes plate current, relay 30 is energized, and armature 53 moves to "a position. Since the charging of capacitor as was terminated at armature 53 when relay 43 was deenergized by opening of the maintaining circuit, capacitor 39 in unit A immediately begins to discharge, although capacitor 39a in unit B remains under charge since the maintaining circuit for unit B is still maintained by its shunt through armature IS in 1) position, even though trip l3 has been opened by the towels leading dge.

Capacitor 39 in unit A, immediately upon interception of trip 12 by the leading edge of the towel as aforesaid, begins to discharge through the following circuit; from capacitor 39 through conductors 55, 53 and 59, armature 5B in a position, resistor 6|, and conductor 62 to capacitor 39. Resistor 5| has a relatively high resistance value, and the capacitor charge leaks off at a relatively slow rate, towel advance in the meantime continuing. When the trailing edge of the towel leaves trip [2, the trip closes, again imposing an overbias on tube 25 so that relay 38 is de-energized, armature 5i? falls to 1) position, but capacitor discharge as above outline continues, except that it now proceeds through resistor 63 instead of resistor 3|. Resistor 63 is of lower resistance than resistor 5|, so that dis charge proceeds at an accelerated rate. The re- -lationship of the combined slow and fast dis- :1 position, and the folding blade solenoid is energized as follows: from L1 through conductor 60, armature 5| in a position, conductor 64,

.armature 22 in a? position, conductors 65 and 66, folding blade operating device l9, and conductor 61 and 68 to L2. A folding operation is thereupon performed on the towel. Operation of the folding blade closes switch 20, energizes device 2|, and results in the movement of switch armature 22 to the b position, adapted to next cooperate with a folding operation controlled by unit B. Snap switch controls l5 and 2| are identical, and will be more fully described later.

As the trailing edge of the towel passed trip II, the snap-over device l5 was energized, asalready understood, throwing switch armature to.

its a position and thereby supplying a shunt circuit for trip |2 so as to permit capacitor 39 to continue discharge at status quo rate. This shunt circuit avoids the inherent defect in known prior devices. In said prior devices of the present general character, if the leading edge of a second towel broke the control trip contact (in this case trip I2) before discharge of the control capacitor (in this case capacitor 33 of unit A) was completed, the discharge reverted to the undesired low rate, thereby throwing the whole operation out of accurate sequence. In the present instance this is prevented by the provision of two distinct control units, in conjunction with selector trip [I and reversible switch armature 22, as will appear.

Assume that a second towel approaches on the conveyor, and its leading edge intercepts trips l2 and I3 while the preceding operation by unit A is still in progress, switch armature l6 being now in a position.

Breaking contact at trip |2 by the second towel has no effect on the operation of unit A (which is still operating on the first towel) because armature I6 is now in the a position, and maintains the over bias on tube 25 through conductors 32 and 70, armature I6 in a position, and conductors 1|, 35, and 36, resistance 29, grid and cathode of the tube and conductor 31. Relay 30 remains de-energized, armature 50 remains in 12 position and discharge continues at the accelerated rate.

Breaking contact at selector trip I by the second towel likewise has no effect on the operation of unit A because the selector trip operates the snap-over device |5 only when contact is made at trip However, when the second towel intercepts trip l3, and breaks contact at that point, it begins discharge of capacitor 390. in unit B by breaking its maintaining charging circuit, as will be fully understood upon consideration of what has already been described with respect to inception of operation of unit A. It will be evident therefore that discharge of capacitors 39 and 39a is now taking place simultaneously, and travel of the first and second towels is being timed simultaneously, but by different units.

At about this time in the progress of the cycle, capacitor 39 in unit A discharges past the critical bias point, and the first towel is folded, at which time operation of folding blade l8 throws switch armature 22 to the 1) position so as to leave it in the circuit associated with armature 5| a of unit B, where it will be adapted to respond next to the discharge of capacitor 39a of unit B.

When the trailing edge of the second towel passes trips |2 and I3, it leaves them in the position in which they were at the beginning of the herein described cycle of activity, since contact at selector trip I I again throws armature l6 back to the 1) position. Folding of the second towel also throws switch armature 22 to its a 7 position. When a third towel goes through, it energizes the circuits previously energized by the first towel, and thus alternate towels will. be operated on respectively alternately by units A and 13.

Another advantage to the use of two alternating units, as shown, is that the interposition of an extremely short article among a succession of relatively long articles, or vice versa, does not disturb the timing sequence. The timing sequence might be disturbed if two extremely short articles follow a maximum length article on the conveyor. This condition is not usually met, and

the apparatus will perform satisfactorily if the minimum length article to be folded is not smaller than about one third of the maximum length article. With this in mind the sequence of long and short articles, in any order, is immaterial. This numerical limitation is dependent on several factors such as the spacing between the trips and the folding blade, the total charge in the charged capacitor, and the respective rates of the capacitor discharges.

The reference numerals in unit B are identical with the numerals applied to respectively corresponding parts in unit A, except that all numerals in unit B are accompanied by the suffix a. To simplify the wiring circuits as far as reasonably possible, we have shown two transformers 28 and 28a with their respective primary and secondary circuits. Obviously one transformer would be used in practice, with any convenient or necessary number of secondary taps. The secondary taps F1-F2 on transformer 28 energize the filaments of tubes 25 and 26. In Fig. 2 the snap-over devices l5 and 2| are illustrated merely schematically. Such devices for reversing an element position at each energization but not at each de-energization, are available commercially, and their specific structure forms no part of the present invention. For completeness of disclosure, however, one such device is shown in Fig. 3, and its operation will now be briefly described.

The device comprises a pair of axially aligned, spaced solenoids l5 and 76 provided with a pair of armatures TI and i8 united by a rod 79. As will appear, the solenoids are energized alternately, so as to move armatures Ti and '18 back and forth. The mid point of a toggle linkage 88, 8| is pivoted at 82 on rod 19. Link 8! also has an intermediate pivot point 83 which is fixed with respect to the solenoids. The corresponding point 84 is lineally movable with respect to pivot 83, and a tension spring 85, having a fixed end at 83, and a movable end at 84, tends to increase the angularity between the links 8ll- 8i. The device therefore constitutes an over-center snap action mechanism, and, in the position shown, if solenoid 15 is energized while solenoid 76 is deenergized, armature 1'! will be moved downwardly into solenoid 15, causing over-center operation of the linkage, and reversal of the position of switch armature it, which is carried on the end of link 8 l.

Alternate energization of solenoids '35 and i6 is accomplished as follows. Closure of selector trip I], as by passage of the trailing edge of a towel closes an electrical circuit from-L1 through conductor 81, contacts of switch 88 through armature 89 on the end of link 88, conductor so, so-

' zation of solenoid coil '15 produces reversal of the over-center linkage, and consequent travel of 8 the switch armature 89 along connector strip 96 towards switch 91. As armature 89 passes the mid point of its travel, it momentarily establishes a circuit connection between strip 96 and a terminal 98 so as to complete an energizing circuit for relay coil as as follows; from In through conductor 95, relay coil 99, conductors Hill and ml to terminal 98, thence through armature 39 to strip 95, conductor 81, and trip It to L1. Energization of relay coil 99 attracts linked armatures as and I02 with the following results.

Armature I82 moves from its 1) position to its a position to set up the following maintaining circuit for relay coil 99; from L2 through conductor 95, relay coil 99, conductors lot and H33, armature it? in a position, conductor Hi4, conducting strip 95, conductor 8-1, and closed trip 1 l to L2. As a result of relay coil 99 being energized armature 93 has moved from its 1) to its a. position, breaking to circuit to solenoid it so as to de-energize it, both solenoids i5 and 16 being at the present time ole-energized.

In the meantime armature 8 9 on link 89 comes to rest at switch 97, at which point it is in position to energize solenoid it at a proper position in the cycle, as will appear.

When the leading edge of a second towel intercepts trip ll, it breaks the maintaining circuit for relay coil 99 and armatures 93 and I02 fall to their b positions. Interception of trip H h no other effect at this time.

When the trailing edge of the second towel passes trip H, permitting it to again close, solenoid I6 is now energized through a circuit from L1 through trip ll, conductor 87, strip 95, armature 88 bridging switch contacts 97, conductor I06, winding of solenoid l6, conductors I07 and 92, armature 93 in 11- position, conductors 94 and 95 to L2.

Energization of solenoid it again snaps the linkage 8ll8l over-center, causing armature 89 to be carried back towards switch 88. At the mid point of its travel it establishes an energizing circuit for relay 99, as before, and relay 99 sets up its own maintaining circuit while solenoid T6 is de-energized by a circuit break at armature 93.

By the use of a device of this nature, each time the circuit is closed at trip H, by passage of the trailing edge of an article, switch armature l6 on the end of link Bl reverses its position, but nothing happens when the circuit is broken at trip I! by the leading edge of an article.

In the circuits shown in Fig. 2, switch armatures l6 and 22 bear a certain phase relationship to each other to the extent that when armature I6 starts in the a. position, armature 22 should start in the 1) position. If, one or other armature should accidentally become reversed so as to be out of phase, with the other the first article thereafter passing through will reverse armature it but will not be folded. Thereafter both armatures will be in proper phase for the second and all subsequent articles.

The trips H, l2 and I3 have been schematically illustrated in Fig. .2 as physically distinct from each other, but all three trips are opened by the leading edge of the moving article, and all three close when the trailing edge of the article leaves them. It will be apparent to those skilled in the art that a single trip could be arranged to carry three sets of electrical contacts, one such set controlling the circuit to selector I5, and the other two sets serving the respective timing circuits to units A and B. In this specification, and the appended claims, the term trip while comprising the conventional device heretofore well known in the art, likewise include any other ar-- rangement wherein a pair of electrical circuitterminals are separated, or moved into contact, responsive to movement of the article. r

WhatIclaimis:

1.:Apparatus of the character 'describedfor effecting a proportionate fold in each of a series of laundry fiatwork articles moving'in longitudinally spaced relationship along a path, comprising a folding device, a pair of substantially iden tical time delay units effective upon said folding device, each unit being independently adapted to control operation of said folding device, a first. timing trip, a second timing trip, and a selector trip, all said trips being disposed adjacent each other in said path whereby to be intercepted by a moving article, electrical circuit means operatively connecting the first said timing trip to one time delay unit, and the second 'said timing trip to the other time delay unit, switch means responsive to operation of said selector trip by a moving article, said switch means being effective alternately, upon the electrical circuit for one said unit and the electrical circuit for the other said unit, whereby interception of the first said timing trip and the selector trip by a moving article institutes a timed control operation by one said time delay unit, and interception of the second said timing trip and the selector trip by the next succeeding moving article institutes a timed control operation by the other said timing unit.

2. Apparatus of the character described for effecting a proportionate fold in each of a series of laundry flatwork articles moving in longitudinally spaced relationship along a path, comprising folding means, a first time control unit a second time control unit, each unit being independently adapted to cause operation of said folding means, first and second folding circuits respectively operatively connecting said first and second time control units with said folding means, a folding selector switch responsive to operating movement of said folding means, and effective alternately upon said first and second folding circuits whereby to render said folding means responsive, alternately to said first and second time control units, a first timing trip, a second timing trip, and a timing selector trip, all three said trips being disposed adjacent each other in said path ahead of said folding means whereby to be intercepted by each moving article, first and second timing circuits respectively connecting the first said timing trip to the first said time control unit, and the second. said timing trip to the second said time control unit, switch means responsive to said timing selector trip and effective alternately upon said first and second timing circuits whereby interception of the first said timing trip and the selector trip by a moving article institutes a time control operation by one said time control unit, and interception of the second said timing trip and the selector trip by the next succeeding moving article institutes a time control operation by the second said time control unit.

3. Apparatus of the character described for effecting a proportionate fold in each of a series of laundry fiatwork articles moving in longitudinally spaced relationship along a path, comprising folding means, a first time control unit, a second time control unit, each unit being independently adapted to cause operation of said folding means, first and second folding circuits re- 10' spectively operatively connecting said first and second time control units with said folding means, a folding selector switch responsive to operating movement of said folding means, and effective alternately upon said first and second folding circuits whereby to render said folding means responsive, alternately to said first and second time control units, a first timing trip, a second timing trip, and a-timing selector trip, all three 5 said trips being'disposed adjacent each other in said path ahead of said folding means whereby to be intercepted by each moving article, first and second timing circuits respectively connecting the first said timing trip to the first said time control unit, and the second said timing trip to the second said time control unit, switch means responsive to said timingv selector trip and efi'ective alternately upon Ssaid'first and second timing circuits whereby interception of the first said timing :trip' and the selector trip by a moving article institutes a time control operation by one said time control unit, and interception of the second said timing trip and the selector trip by the next succeeding moving article institutes a time control operation by the second said time control unit, said folding blade selector and said timing selector having a definite positional phase relationship to each other whereby, when the first said timing unit completes a timing operation responsive to interception of the first said timing trip and selector trip, said folding selector is in suitable position to close said first folding circuit with consequent operation of said folding means, and when the second said timing unit completes a timing operation responsive to interception of the second said timing trip and the said selector trip, said folding selector is in suitable position to close said second folding circuit with consequent operation of said folding means with respect to the next succeeding article.

4. Apparatus of the character described including operation-performing means for the execution of a timed operation on each of a series of spaced, moving articles, comprising a first time control unit and a second time control unit, each such time control unit having, as an element thereof, an electrical capacitor, each said capacitor having its respective electrical control circuits, and being adapted by controlled change in the charge thereof to control the said timed operation, and each such control unit being responsive to article travel past a control zone, se lector switch means located in said control zone, and responsive to passage of each article past said control zone, said selector switch means being operatively effective upon said electrical control circuits and thereby upon the two said time control units in turn, so as to initiate a complete timed operation, first by the first said time control unit on one article in said series, and next by the second said time control unit on the next article in said series, each such time control unit having respective electrical circuit connections with said operation-performing means whereby completion of the timed operation by each time control unit in turn is effective upon said operation-performing means to produce operation thereof.

5. Apparatus of the character described including operation-performing means for the execution of a timed operation on each of a series of spaced, moving articles, comprising a first time control unit and a second time control unit, each such time control unit having, as an element thereof, an electrical capacitor, each said capacitor having its respective electrical control cirwits, and being adapted by controlled change in the charge thereof to control the said timed operation, and each such control unit being responsive to article travel past a control zone, se-

lector switch means located in said control zone,

trol unit on one article in said series, and nextby the second said time control unit on the next article in said series, a second selector switch means having respective electrical circuit conneotions with each time control unit, and also with said operation-performing means, said second selector switch being operatively responsive to operation of said operation performing means so as to close the circuit first to one said time control unit on one operation of said operationperforming means, and then to close the circuit to the other said time control unit on the next operation of said operation-performing means, whereby completion of the timed operation by each time control unit in turn is efieotive upon said operation-performing means to produce operation thereof.

THOMAS J. DORAN.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,581,753 Mayer Apr. 20, 1926 1,697,010 Jones et al Jan. 1, 1929 20 2,362,753 Huck Nov. 14, 1944 

